Abstract No.:	1264
Title:	Mechanical properties of WC/Co coatings prepared by cold spraying
Authors:	Junya Kitamura* / Fujimi Incorporated, Japan Kazuto Sato / FUJIMI INCORPORATED, Japan Isao Aoki/ FUJIMI INCORPORATED, Japan Kazuhiko Sakaki/ Shinshu University, Japan Muneaki Takahata/ Shinshu University, Japan Yasuo Shimizu/ Shinshu University, Japan
Abstract:	Some previous studies by other researchers have clarified that WC/Co cermet coatings can be prepared using cold spraying in spite of unmelted powder during spraying process. These studies also have showed that the coatings have high density (low porosity) and high hardness. However, other mechanical properties, such as wear resistance, are no reported. Wear resistance of WC/Co cermet coatings prepared by cold spraying have been investigated in this study. We have studied the influence of cobalt contents (12~25wt.%), WC particle size (0.2 and 2.0 micrometers) and agglomerated-and-sintered powder size (-20+0 and -45+15 micrometers) on abrasive wear resistance, micro hardness and coating structure, in detail. It has been found that both smaller WC particle and decrease of cobalt content are effective to produce dense, hard and highly wear resistant coating. Smaller powder size is also favorable to make a coating with high mechanical properties. As a result, the cold sprayed coating from WC(0.2 micron)/12%Co with powder size of -20+0 micron has best mechanical properties within this study. This coating has high uniformity and high density with little pores compared to conventional HVOF sprayed coatings. Abrasive wear resistance of the cold sprayed coating, investigated using Suga-abrasion tester, has been almost comparable to HVOF sprayed coating prepared from same feedstock. Strong correlation is also seen between Vickers hardness and abrasive wear resistance. Microstructural analysis suggests that further improvement of coating uniformity by decrease of small pores with the size of sub micron and homogeneous dispersion of WC grains in the cobalt matrix is required to improve the mechanical properties.

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